Red wine research DOESN’T show it can ‘reduce breast cancer risk’

Women reading Monday morning’s news may be forgiven for rejoicing at the idea that – according to at least one paper – “a regular glass of red wine can help women ward off breast cancer”.

We’ve been here before, and stories of alleged anti-cancer benefits of red wine appear regularly in the media. But they all miss a fundamental point: as well as small quantities of potentially beneficial chemicals, red wine also contains large amounts of one that definitely causes cancer: alcohol.

As well as this the study behind the headlines (press released here), written by a team at Cedars-Sinai Medical Centre in the US, only looked at the relative effects of red and white wine on women’s hormone levels, rather than studying breast cancer rates. And there were just 36 women on the study, who were only followed up for two months.

So, unfortunately, we don’t think that the data in their paper are anywhere near strong enough to change the recommendations about what people should or shouldn’t do to influence their cancer risk.

It’s also ironic that this research comes out on the day the House of Commons science & technology committee said that it felt there was confusion about drinking recommendations, and that people should try to stay alcohol-free on at least two days a week.

Let’s take a quick look at the breast cancer paper, and the bigger picture of alcohol and breast cancer.

What did the researchers do?

The researchers asked a group of 36 healthy premenopausal women to drink about three units of either red or white wine every day during one monthly menstrual cycle, and then three units of the other colour wine for their next cycle. Half the women drank red wine first, the other half started on white.

The researchers took samples of the women’s blood throughout the study, measured hormone levels in them, and looked at how they changed when women drank different coloured wines.

The variations they found in other hormones – including oestrogen itself – weren’t statistically significant (which is another way of saying the researchers couldn’t be sure whether these results were ‘real’ or just due to randomness).

How did they interpret this?

According to the researchers, the fact that red wine altered the levels of these particular hormones is consistent with the idea that it might contain one or more chemicals that blocks a hormone called aromatase, which is a key player in the manufacture of our sex hormones.

Aromatase is also the target of certain breast cancer drugs like anastrozole, as shutting off its action lowers the production of oestrogen (which can encourage breast cancer cells to grow).

But unfortunately, the press release that accompanied the research went on to say that this means that drinking red wine instead of white ‘can protect against breast cancer’. The lead researcher, Chrisandra Shufelt, said about the results: “If you were to have a glass of wine with dinner, you may want to consider a glass of red. Switching may shift your risk.”

This is – in our opinion – rather overstating things. The finding that hormone levels fluctuate over a couple of months, while intriguing, says nothing about whether this counteracts the harmful effects of the alcohol in the wine. And it ignores a large number of other, longer, larger studies that show that cases of breast cancer are more common among women who drink even small quantities of alcohol – of any type.

So what do other studies say?

We’re not short of large studies that link alcohol to breast cancer, or otherwise contradict the results of this study.

In 2006, the Europe-wide EPIC study found that overall alcohol consumption increased the levels of sex hormones in drinkers’ blood.

In 2007, the World Health Organisation felt that the totality of the evidence on alcohol and breast cancer was strong enough to say that alcohol ‘caused’ the disease, rather than just being ‘linked’ to it.

In 2009, the UK’s Million Women Study which, as its name suggests, is following the fates of rather more than thirty-six women, found that drinking wine was just as bad – in breast cancer terms – as drinking other types of alcohol, and that drinking even moderate amounts could up the risk of breast cancer.

In August last year, the Cancer Research UK-funded Endogenous Hormones and Breast Cancer Collaborative Group, based in Oxford, pulled together the results from 13 large studies of the effects of alcohol on sex hormones in post-menopausal women, and concluded that “the increases in sex hormone concentrations associated with alcohol consumption might contribute to the increase in breast cancer risk with alcohol consumption”. They’re now investigating the effects of alcohol on premenopausal women’s sex hormones.

Finally, late last year, we published an analysis of the factors linked to various cancers, and showed that more than 6 per cent of breast cancers in women in the UK in 2010 were linked to alcohol consumption – as our blog post and accompanying graphic shows.

So in short, there’s plenty of evidence that cutting back on alcohol – of any type – is a sensible and easy way to reduce your chances of breast cancer later in life (although there’s never any guarantee). Cutting back on alcohol is beneficial for a whole range of other types of cancer, and other diseases too – particularly liver problems. So today’s government report, recommending a review of how alcohol guidelines are drawn up and communicated, is welcome.

But in the dark, gloomy slog of post-festive January, it’s understandable that people – including press officers and journalists – would want to spread a little cheer to get us all through to spring.

And it’s nice to think that choosing a Merlot or a Cabernet Sauvignon instead of a Chablis or Chardonnay might be somehow better for us. But sadly, recommending that women drink red wine regularly to protect themselves against cancer just isn’t scientific, whatever we might want to believe.

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